Ink-jet printing systems have utilized intermediate transfer surfaces, such as that disclosed in U.S. Pat. No. 5,389,958 for IMAGING PROCESS, assigned to the assignee of the present application. This patent discloses a system wherein an intermediate transfer drum is employed with a print head. A final receiving surface such as paper is brought into contact with a liquid intermediate transfer surface on the intermediate transfer drum after an ink image has been placed thereon by the nozzles in the print head. The image is then transferred to the final receiving surface. The intermediate transfer surface is cleaned and reapplied prior to the next image being formed on the transfer surface.
Imaging systems using a liquid intermediate transfer surface require some sort of applicator assembly for applying and metering the fluid onto the transfer drum support surface. One such applicator assembly is disclosed is copending U.S. patent application Ser. No. 08/382,453, assigned to the assignee of the present application. This application discloses an applicator assembly that is housed in a replaceable transfer drum maintenance cartridge. The applicator assembly uses a liquid impregnated wick as a contact medium to apply the liquid onto the transfer drum support surface and to remove foreign matter from the support surface. The liquid is stored in a reservoir adjacent to the applicator assembly. The release of the liquid from the reservoir is actuated by the movement of the wick assembly upwardly along a valve opening track as the wick assembly moves toward the transfer drum support surface. The applicator assembly includes a hydrodynamic wiper blade that uniformly meters and distributes the liquid intermediate transfer surface over the support surface and incorporates a dam to contain and distribute a sufficient amount of liquid onto the support surface.
While the applicator assembly described in the above application performs well when used in conjunction with printers printing on A-size media (8.5 in..times.11.0 in.; 21.59 cm..times.27.94 cm.), it is not as well suited for use in B-size (11.0.times.17.0 in.; 21.59 cm..times.27.94 cm.) and larger printers. The larger surface area of the media handled by these printers requires a correspondingly larger amount of liquid to create the intermediate transfer surface. Accordingly, the volummetric capacity of the reservoir containing the liquid must increase, as well as the surface area of the wick that applies the liquid.
As explained in the above-referenced copending application, prior to installation of the drum maintenance cartridge in a printer, the liquid is securely contained in the reservoir and does not flow to the wick in the applicator assembly. Upon insertion of the cartridge into a printer, a valve is opened and the liquid begins flowing to the wick. To allow the wick to become sufficiently saturated with the liquid for proper operation, printing is disabled for a predetermined period after a new cartridge is installed in a printer. This delay, or "time-to-first-print," must be as short as possible to avoid user dissatisfaction. Thus, especially in B-size and larger printers, it is desirable to rapidly communicate liquid from the reservoir to the wick upon insertion of the cartridge to minimize the time-to-first-print. Also, where an oil is used as the liquid for the intermediate transfer layer, it is especially important to have a simple and reliable, yet relatively inexpensive supply system that does not leak or erratically dispense the oil.
What is needed is a liquid supply system for an intermediate transfer surface application system that overcomes the drawbacks of previous supply systems. Such a system must speed the initial flow of the liquid from the reservoir to the applicator assembly to minimize the time-to-first-print. At the same time, such a system must simply and reliably deliver a precise amount of liquid to the wick without leaking or generating undesirable pressure in the reservoir or connecting tubing.